This invention relates generally to methods, devices and apparatus for laying cables. More particularly, this invention relates to methods, devices and apparatus for laying cables additionally or newly inside and/or outside a building, a factory, a station or the like.
Presently, a plurality of cables are laid on a installed cable ladder or ladders(L).
Conventionally, as shown in FIG. 102, cable layers pull up and drag a cable(C) on cable ladders(L).
Alternatively, as shown in FIGS. 103 and 104, cable layers first lay a messenger rope(R) through a cable ladder(L). The messenger rope(R) is then connected to the cable(C) and dragged by a traction motor(M).
In order to lay a cable(C) at a high position by the process as shown in FIG. 102, a greater number of cable layers are required for the operation, and ladder hanging bolts(B) often hinder the operation, requiring more time and cost for the operation.
In order to lay a cable(C) by the processes as shown in FIGS. 103 and 104, a messenger rope(R) must be dragged by cable layers who have to change positions as required, and in order to lay a plurality of cables(C), these processes have to be repeated. Ladder hanging bolts(B) hinder the operation in these cases as well.
Japanese patent publication No. 63-144707, laid open unexamined, discloses a resolution to those problems, in which a guide wire is installed like a loop preparedly on a cable ladder. A messenger rope and a cable connected to the messenger rope are dragged on the cable ladder as the guide wire connected to the messenger rope is dragged. This device, however, requires a complicated set of apparatus and their strenuous installation.
Japanese patent publication Nos. 61-23182 and 63-18911, laid open unexamined, also disclose a resolution to the aforementioned problems. The devices disclosed in those publications use draggers at certain intervals along the cable route which pass on a guide bar to which a cable is connected.
This type of device does not require the use of a messenger rope, however, a plurality of draggers and their strenuous installation are required. The removal work of the draggers is also strenuous. The apparatus to securely guide a guide bar from dragger to dragger are costly as well.
Therefore, it has been desired to have a method, a device and an apparatus which enable an efficient and easy operation for laying a cable or cables which are often as long as 100 meters.